In recent years, portable electronic devices such as smart phones, personal digital assistant (PDAs), tablet terminals and notebook personal computers have been required to have a lighter, thinner and smaller housing in order to decrease their sizes and weights. Accordingly, antenna devices for the portable electronic devices have also been required to be made more compact. Also, in recent years, the portable electronic device have been required capable of performing communication in a wider frequency band, in order that they can each communicate with a plurality of wireless systems having different frequency bands.
In view of the above, antenna devices have been proposed in which in addition to a folded-type monopole element, a second monopole element and a passive element are added in order to widen a resonant band. Also, antenna devices have been proposed in which a capacitor element is provided close to a feeding point of a folded-type monopole element provided with a stub in order to widen an operation frequency band.